Serum cholinesterase

How the Test is Performed:
Adult or child:
Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding .

Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The sample is then taken to the laboratory for evaluation.

How to Prepare:
Adults:
No special preparation is necessary for this test.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:



How it Feels:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing .

Risks:
Risks associated with venipuncture are slight:

  • excessive bleeding
  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins



Why this Test is Performed:
This test is usually performed before electroconvulsive therapy ( ECT ). A paralyzing agent called succinylcholine is administered before ECT to prevent a full blown seizure during treatment. Your health care provider can determine your potential response to succinylcholine with this test.

The test may also be performed to identify exposure to organophosphates that inactivate cholinesterases, or rarely to identify liver disease .

Normal Values:
The normal value of pseudocholinesterase depends on the technique used for evaluation. The value typically falls between 8 and 18 U/ml.

Note: U/ml = units per milliliter

Abnormal Results:
Decreased pseudocholinesterase levels may indicate:



Cost:
Information not available.

Special Considerations:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.